More than 800 potentially lethal weapons were seized as police launched a major crackdown to snuff out any supply line to terrorists.
Officers recovered 833 firearms including machine guns and assault rifles as well as thousands of rounds of ammunition in just a month.
Scores of suspects were arrested during the operation, which started in October with the aim of preventing criminals and terrorists gaining access to illegal firearms.
The joint initiative was conducted by the National Crime Agency (NCA) and counter-terrorism police as part of efforts to clamp down on any connection between organised gangs and extremists.
Concern over the danger of terrorists getting hold of guns increased in the wake of the Paris attacks in November 2015.
Investigators did not identify any clear link to terrorism as part of the activity but it did yield a "handful" of counter-terrorism leads.
Detective Superintendent Nick Wilcox, of National Counter Terrorism Policing (NCTP), said: "Counter terrorism officers continue to plan and prepare in light of world events such as the attacks in Paris - but we want to remain on the front-foot and stop terrorists obtaining guns in the first place.
"Low firearms availability is a major advantage in the UK."
Of the firearms seized during the four-week operation, 379 could be considered viable, 14 were non-viable while a further 440 are awaiting assessment.
The haul included a fully-loaded AK74 assault rifle and a Skorpion submachine gun.
Some firearms were seized from registered dealers who had their licenses revoked and weapons confiscated, usually for inadequate certification.
Officers also recovered 4,385 rounds of ammunition and over 100 additional potential weapons such as knives, as well as 176lb (80kg) of illegal drugs and more than half a million pounds in cash.
Of the 282 people arrested, 111 related to suspected firearms offences. Sixteen arrests have resulted in a charge, 43 people have been bailed while 15 were released to face no further action.
NCA deputy director Chris McKeogh, who led the operation, said: "The surge of activity across the whole of the UK has yielded significant results - from the seizure of illegally held firearms and ammunition, to the number of reports we received from members of the public via Crimestoppers.
"Collectively, we will build on what we achieved in this short period of time to ensure that we develop the best intelligence we can about the firearms cross-over between organised crime and terrorism."
He hailed the public response to the campaign, adding: "This is not over though. One gun in the wrong hands is too many, so please think hard and if you know something, pick up the phone anonymously."